Multi-scale interactions driving 2010 extreme blizzard in Xinjiang

During the winter of 2010 (January to February), northern Xinjiang experienced record-breaking snowstorms. Accompanied by frequent, persistent snowfall, the temperature also fluctuated greatly, resulting in repeated melting and freezing of the snow. Electricity and transportation systems were severely disrupted and almost halted. The snowstorms were caused by two types of persistent snowfall: warm-sector blizzards and cold-front blizzards. Using the recently developed multi-scale window transform and multi-scale energy analysis methods, we identified the key circulation systems and their multi-scale interactions responsible for these snowstorms. The results demonstrate that the key circulation system driving the three warm-sector blizzards in January was the European blocking of high pressure. In these blizzards, warm and moist air from the Central Asian jet stream was transported northeastward and converged with cold air from northern Xinjiang (ahead of the high-pressure ridge), resulting in the formation of warm sector blizzards. The original circulation field was reconstructed onto three scale windows: Seasonal window, BH window (blocking high window), and synoptic window. The BH subspace revealed that during the three blizzard events, the Siberian blocking high-pressure system weakened and merged with the European blocking high-pressure system, causing the European blocking high-pressure system to re-strengthen and persist for an extended period. This suggests that the three blocking-high processes are essentially the three stages of a single continuous event. It was found that the maintenance of blocking high results from canonical transfers through barotropic instabilities in this region, which extract kinetic energy (KE) from the synoptic scale reservoir. The key circulation system driving the February cold-front blizzards was an anomalous cold vortex over the Siberian region, forming part of a stationary wave train extending from the Atlantic to East Asia. Unlike previous studies that attributed blizzards to the southward movement of cold polar air, this study found that this movement only initiates the cooling process. The primary cause of prolonged cold-front snowstorms is sustained stationary wave trains. The maintenance of a stationary wave train results from canonical transfers through baroclinic instability in this region, which extracts available potential energy from the seasonal scale reservoir.